In another experiment, in the same report, two additional male rabbits were injected with
10 mg progesterone every other day for 28 days. Two control males were included but
the authors did not report if the control males were treated with vehicle only or untreated.
One of the progesterone-treated rabbits showed reduced libido shortly after beginning of
the treatment. Average total sperm counts and semen volume were significantly reduced
from the 15
th
through 27
th
week. Both treated males were azoospermic from the 19
th
through 21
st
week of treatment. Decrease in semen volume was partially due to a lack of
gelatinous material, produced by glandulae vesiculaes (seminal vesicules).
In the 1958 report (Heller et al. 1958), one group of four subject received daily
intramuscular injection of one dose of 50 mg progesterone for 10 weeks. Each of three
other groups (5 men per group) was given two daily oral doses of nilevar
(norethandralone), norlutin (norethindrone), or enovid (a combination birth control agent
containing norethynodrel and mestranol). Testicular biopsies, semen samples, and urine
samples for determination of levels of gonadotrophins, estrogens, pregnanediol, and 17-ketosteroids were obtained from each subject at pretreatment and immediately before the end of treatment. During the treatment, sperm counts and motility were evaluated at 1- or
2-week intervals.
The authors found that progesterone and the three other progestagen treatments caused
azoospermia in all subjects. Decreases in sperm motility and sperm counts in
progesterone-treated men started after the second week of treatment and azoospermia was
reached in Week 10. All subjects also lost libido and had difficulty in producing semen
samples by masturbation after three to four weeks of treatment. At the end of treatment,
testicular size and absolute number of mature sperm forms per tubule in testicular
biopsies from progesterone-treated men was decreased. Gynecomastia occurred in two of
four treated men. As determined at the end of treatment, progesterone led to decreases in
17-ketosteroid excretion in urine, but there was no change in urinary excretion of
gonadotrophins (measured in a whole animal bioassay), estrogens, or pregnanediol.
progeshid5.pdf (385 KB)